This invention relates generally to steam turbines and, more particularly, to a nozzle box for use with a steam turbine.
At least some known steam turbines include a nozzle box that facilitates channeling fluid towards a first stage of a turbine. At least some known nozzle boxes each include a plurality of inlets, an annular region, and a plurality of discharge nozzles. The inlets channel steam into the annular region. Because the steam discharged from each inlet typically varies in pressure, the annular region facilitates mixing the steam discharged from the various inlets to provide a substantially evenly distributed pressure of steam throughout the region. The steam is discharged from the annular region through the plurality of nozzles towards the first stage of turbine rotors.
The annular regions of at least some known nozzle boxes have a circular cross-section. Moreover, at least some known nozzle box inlets are oriented such that steam is discharged into the annular region in a direction that is substantially perpendicular to a line extending tangentially to the region. However, the circular cross-section of the annular region and the orientation of the inlets may result in an uneven flow distribution throughout the annular region such that portions of the annular region may be deprived of steam flow. Such uneven flow may create an uneven steam pressure distribution which may induce vibrations within the turbine when the steam is discharged through the nozzles at uneven pressures. Continued operation with such vibrations may decrease the useful life of the turbine and/or increase maintenance costs associated with the turbine.